The invention relates to a device with at least one movement unit having coupled thereto at least three adjusting devices by a respective first connecting member and connected by a respective second connecting member, positioned at a spacing to the respective first connecting member, to a frame structure in a pivotable manner. Due to the first and second connecting members, the adjusting devices are freely pivotable relative to the movement unit and to the frame.
Devices for numerically path-controlled manufacturing apparatus are known which are suitable for the five-axis machining, respectively, positioning of a tool or a measuring device relative to a work piece or to an object in space. Conventional machining concepts, especially for straight movements, have the required constructive features such as Cartesian axis arrangement of advancement components. Modern manufacturing apparatus correspond with respect to their mechanical basic design and their machine kinematics substantially to these proven, highly developed and successfully employed machine concepts. For each degree of freedom of movement of the machine in the x, y, and z directions different constructions of the axis components were constructed and the straight advancement movement was adjusted. Each of these components, in general, has different stiffness as a function of their design and the employed machine and drive elements. Due to the open machine kinematics the yielding, respectively, deformations are additive, caused by all components of the machine within the flow of force so that the total stiffness of the machine is below the stiffness of its weakest mechanical member. This causes in machining devices designed for high stiffness correspondingly large component cross-sections with high moved masses.
A disadvantage of the conventional five-axis machines are the time-consuming and generally manually performed steps for adjusting and aligning during start-up and adjusting of the machine when manufacturing tolerances are surpassed. While errors in the x, y, and z directions for Cartesian machine designs can be compensated control-technologically or by control adjustment, angle deviations (yawing, pitching, rolling) can only be adjusted manually with time-consuming corrective measures of the machine geometry by adjusting or post-machining steps.
This is contrasted by new concepts for manufacturing and measuring devices for positioning a tool or a measuring device relative to a workpiece or object by closed rod linkage kinematics on tripod or hexapod basis (European Patent 0 202 206 B1, respectively, U.S. Pat. No. 5,401,128; WO 92/17313 A1, U.S. Pat. No. 5,388,935; European Patent Application 0 589 565 A2, U.S. Pat. No. 5,392,663; European Patent 0 534 585). The development of hexapodal machines have lead increasingly to manufacturing devices which have considerable disadvantages relative to conventional machining concepts. Examples for this are less expensive manufacture, minimal number of different components, simple mounting, and a geometry development and correction by software. However, this requires a considerable expenditure with respect to controlling and governing, since even for linear movements all axes must be controlled simultaneously. A further disadvantage of currently existing tool, measuring, and mounting apparatus is that a high expenditure with regard to peripheral units is required in order to perform an automatic tool change, respectively, workpiece exchange as well as workpiece supply and workpiece clamping. This results in high apparatus costs. Hexapodal machines have great degrees of freedom of movement so that complicated tool changing mechanisms are not required and it is instead possible to work with pick up systems.
In the known tripodal and hexapodal machines and manufacturing devices the respective arrangement of the rods which allow movement of a platform relative to a stationary base by changing the length of the participating rods results in a tension/pressure changing load on the rods. This requires a complicated design and precise manufacture of the connecting members which are arranged as coupling elements at the two ends of the rods. In these devices a non-linear stiffness behavior of the device, when load reversal occurs, can be observed. Furthermore, dynamic instabilities of the rods especially under pressure load can be observed. Furthermore, a pretension of the movement unit for adjusting the stiffness is not possible. For employing these new machining concepts in manufacture, high stiffness and linear transmission behavior are the basic requirements for highly precise manufacturing devices and are thus important and, in the end, market-controlling properties.
It is an object of the invention to embody the aforementioned device such that high stiffness and linear transmission behavior is ensured.